The oxygen sensor used in automobiles to control the air/fuel mixtures and other industrial applications employs a zirconia ceramic element. It is desirable to fabricate the element in the most economical manner feasible, consistent with good operating performance and longevity. Isopressing is a popular method employed in the manufacture of cylindrical shapes characteristic of the oxygen sensor element. Isopressing produces a pre-form in the approximate shape of the element, which must be machined to the required shape before densification by sintering. The machining step represents an extra operation in the manufacturing process, adding cost to the overall process. In addition, a certain yield loss is associated with machining due to breakage of some of the pre-forms during the machining process. The yield loss due to breakage contributes to a higher manufacturing cost of the final product.
Injection molding is a net-shape forming process, and, therefore, offers considerable advantages over processes that require additional machining and finishing operations in order to produce a ceramic part.